.\" Copyright (c) 2006-2008 Stanislav Sedov <stas@FreeBSD.org>
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.Dd June 20, 2014
.Dt CPUCTL 4
.Os
.Sh NAME
.Nm cpuctl
.Nd cpuctl pseudo device
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your kernel
configuration file:
.Bd -ragged -offset indent
.Cd "device cpuctl"
.Ed
.Pp
Alternatively, to load the driver as a module
at boot time, place the following in
.Xr loader.conf 5 :
.Bd -literal -offset indent
cpuctl_load="YES"
.Ed
.Sh DESCRIPTION
The special device
.Pa /dev/cpuctl
presents interface to the system CPU.
It provides functionality to retrieve
CPUID information, read/write machine specific registers (MSR) and perform
CPU firmware updates.
.Pp
For each CPU present in the system, the special device
.Pa /dev/cpuctl%d
with the appropriate index will be created.
For multicore CPUs such a
special device will be created for each core.
.Pp
Currently, only i386 and amd64 processors are
supported.
.Sh IOCTL INTERFACE
All of the supported operations are invoked using the
.Xr ioctl 2
system call.
Currently, the following ioctls are defined:
.Bl -tag -width CPUCTL_CPUID_COUNT
.It Dv CPUCTL_RDMSR Fa cpuctl_msr_args_t *args
.It Dv CPUCTL_WRMSR Fa cpuctl_msr_args_t *args
Read/write CPU machine specific register.
The
.Vt cpuctl_msr_args_t
structure is defined in
.In sys/cpuctl.h
as:
.Bd -literal
typedef struct {
	int		msr;	/* MSR to read */
	uint64_t	data;
} cpuctl_msr_args_t;
.Ed
.It Dv CPUCTL_MSRSBIT Fa cpuctl_msr_args_t *args
.It Dv CPUCTL_MSRCBIT Fa cpuctl_msr_args_t *args
Set/clear MSR bits according to the mask given in the
.Va data
field.
.It Dv CPUCTL_CPUID Fa cpuctl_cpuid_args_t *args
Retrieve CPUID information.
Arguments are supplied in the following structure:
.Bd -literal
typedef struct {
	int		level;		/* CPUID level */
	uint32_t	data[4];
} cpuctl_cpuid_args_t;
.Ed
It is equivalent to the
.Dv CPUCTL_CPUID_COUNT
request with
.Va level_type
set to 0.
.It Dv CPUCTL_CPUID_COUNT Fa cpuctl_cpuid_count_args_t *args
Retrieve CPUID information.
Arguments are supplied in the following structure:
.Bd -literal
typedef struct {
	int		level;		/* CPUID level */
	int		level_type;	/* CPUID level type */
	uint32_t	data[4];
} cpuctl_cpuid_count_args_t;
.Ed
The
.Va level
field indicates the CPUID level to retrieve,
it is loaded into the
.Va %eax
register before the CPUID instruction is executed,
The
.Va level_type
field indicates the CPUID level type to retrieve,
it is loaded into the
.Va %ecx
register.
.Pp
The
.Va data
field is used to store the received CPUID data.
That is,
.Va data[0]
contains the value of
.Va %eax
register after the CPUID instruction is executed,
.Va data[1]
is for
.Va %ebx ,
.Va data[2]
for
.Va %ecx ,
and
.Va data[3]
for
.Va %edx .
.It Dv CPUCTL_UPDATE cpuctl_update_args_t *args
Update CPU firmware (microcode).
The structure is defined in
.In sys/cpuctl.h
as:
.Bd -literal
typedef struct {
	void	*data;
	size_t	size;
} cpuctl_update_args_t;
.Ed
.Pp
The
.Va data
field should point to the firmware image of size
.Va size .
.El
.Pp
For additional information refer to
.Pa cpuctl.h .
.Sh FILES
.Bl -tag -width /dev/cpuctl -compact
.It Pa /dev/cpuctl
.El
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er ENXIO
The operation requested is not supported by the device (e.g., unsupported
architecture or the CPU is disabled).
.It Bq Er EINVAL
Incorrect request was supplied, or microcode image is not correct.
.It Bq Er ENOMEM
No physical memory was available to complete the request.
.It Bq Er EFAULT
The firmware image address points outside the process address space.
.El
.Sh SEE ALSO
.Xr hwpmc 4 ,
.Xr cpucontrol 8
.Sh HISTORY
The
.Nm
driver first appeared in
.Fx 7.2 .
.Sh AUTHORS
The
.Nm
module and this manual page were written by
.An Stanislav Sedov Aq Mt stas@FreeBSD.org .
.Sh BUGS
Yes, probably, report if any.
